How Chrome’s “Tab Freezing” Will Save CPU and Battery

Google is working on a new “Tab Freeze” feature for Chrome, which will pause (freeze) tabs you're not using. That means lower CPU usage, a faster browser, and longer life on a laptop or convertible.

The Problem: Too Many Tabs

If you only had a single tab open at all times, Chrome would only need to render one web page at once. But you probably have more. Even while you're not using them, each tab you have open in Chrome contains an open web page. That web page uses system memory. Any scripts and other active content on it continue running, too, which means the web page can use CPU resources in the background.

In some ways, this is good: Even if you switch tabs, a tab can continue playing audio or updating itself in the background. When you switch back to it, you don't need to wait for the web page to reload it's instant.

But it can be bad. If you have a large number of tabs open or even just a small number of tabs containing heavy web pages they can use a lot of system resources, filling up your memory, taking up CPU cycles, making Chrome less responsive, and draining your . That's why Chrome's engineers created Tab Discarding and, now, Tab Freezing. They're related features, but do different things in different situations.

How Tab Discarding Saves Your RAM

Tab Discarding was added back in 2015. This is a “memory-saving” feature, as Google puts it. In short, if your computer is low on memory, Chrome will automatically “discard” the contents of “uninteresting” tabs. Chrome won't automatically discard a tab if you're interacting with it, but that background tab you haven't interacted with in hours is a prime target.

When a tab's contents are discarded, it's removed from your system's memory, and the state is saved to disk. Nothing changes in Chrome's interface the tab appears on your tab bar and looks normal. But, when you click it and switch to it, you'll see Chrome take a moment to quickly reload the page and get you back to where you were.

This slight delay is why Chrome only discards tab when your system's memory is “running pretty low.” It's good to use your RAM for caching. But automatically discarding a tab and quickly reopening it is better than forcing Chrome's user's to bookmark and close tabs manually.

When a tab is discarded, its process actually vanishes from Chrome's built-in Task Manager, and you won't see its memory used by Chrome anymore. When you click it to reload it, it starts up again.

How Tab Freezing Will Your CPU (and Battery)

Tab freezing is different from tab discarding. When a tab is frozen, its contents stay in your system's memory. However, the tab's contents will be “frozen.” The web page in the tab won't be able to use CPU or perform actions in the background. For example, let's say you have a heavy web page open in a tab somewhere, and it's continually running scripts. After a while, Chrome will automatically “freeze” it and stop it from performing actions until you interact with it again. Those are the basics, and Google will likely explain how it works in much more detail soon.

Tab Freezing is an experimental feature. It's built into current stable versions of Chrome 77, but can only be initiated manually. In Chrome Canary builds of the upcoming Chrome 79, Chrome will be able to automatically freeze tabs just like it can automatically discard them.

In Chrome Canary, several options are available for tab freezing if you head to chrome://flags and search for “Tab Freeze.” With this option enabled, Chrome will automatically freeze “eligible” tabs after they've been in the background for five minutes. Depending on which option you choose, Chrome can either leave them frozen or unfreeze them for ten seconds every fifteen minutes just enough time to sync with a server or get a bit of work done if they need it. Google is clearly testing which option is best.

While tab freezing is an experimental feature, it's almost certainly coming to stable versions of Chrome sometime soon in some form, at least. The options in Chrome Canary were spotted by TechNews.

How to Play With Tab Freezing (and Discarding) Today

The current stable version of Chrome lets you play with both features if you want to know how they work. Just typechrome://discards in Chrome's Omnibox and press Enter.

You'll see a diagnostic page with a list of your open tabs and whether they can be frozen or discarded. On the right side of the page, you'll see action links to “Freeze” and “Discard” each tab.

You can test it out to see the difference yourself. For example, if you launch YouTube and start playing a video, clicking “Freeze” for that tab will pause the video playback but not remove the YouTube tab's contents from memory in the Task Manager. Clicking “Discard” instead will pause video playback and remove the tab's contents from memory you'll see it vanish if you open Chrome's Task Manager. Clicking “Load” will reload the tab's contents to memory.

Why Discarding and Freezing Are So Useful

In other words, if your system's memory is becoming full, Chrome will discard tabs you're not using to free up space. It'll silently reload them when you click the tab, but you'll notice the page loading for a split second. There's no need for Chrome to discard tabs while you have plenty of memory Chrome is using that memory as a cache rather than leaving it empty. This speeds things up.

But, even if you have a lot of memory, Chrome will soon look at freezing tabs you're not interacting with to CPU time and battery power, potentially making Chrome and the other applications on your system more responsive. It will still keep them in memory that way, when you reactivate a frozen tab by switching to it, the web page in the tab is ready to use as quickly as possible.

If Chrome needs to free up some memory, it might discard a frozen tab. But you can't freeze a discarded tab: It's already been removed from memory and isn't truly open, so it can't perform any actions in the background.

Now that the upcoming version of Microsoft Edge will be based on Chromium, Google's work on Chrome will also make Windows 10's default web browser better. Expect future versions of Edge to start freezing tabs automatically, too.

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